The present invention relates in general to video cassette recorders and camcorders, which are hereafter referred to as VCRS, and to the videocassettes which these VCRs use for recording and playing back video and audio signals. More specifically the invention relates to VCRs which record and playback in the S-video mode. These S-video compatible VCRs can record in one or more of the standard formats which include VHS, 8 mm and VHS-C. The same S-video compatible VCRs also record and playback in one or more of the S-video modes which include SVHS,Hi8 mm and SVHS-C. Video signals recorded in the standard formats have a horizontal resolution of approximately 240 lines and are recorded as NTSC which is a composite signal where the luminance and chroma signals are combined. Video signals recorded in the S-video formats have a horizontal resolution of approximately 410 lines and are recorded as S-video signals where the luminance and chroma signals are recorded separately and carried on separate conductors. The S-video formats are superior to standard formats in video picture resolution and in signal degradation through successive editing and processing.
The VCR manufacturers who developed S-video format VCRs specified that S-video signals should be recorded on higher quality tape than the standard formats. To this end these same manufacturers designed the S-video VCRs to include a mechanical limit switch which detects the presence or absence of a record enable I.D. hole in the videocassette. Videocassettes which are sold as S-video compatible have an integrally molded the S-video record enable I.D. hole. When a videocassette that has the record enable I.D. h hole is loaded into a S-video compatible VCR the mechanical limit switch actuator pin goes into the same I.D. hole. The limit switch remains unactuated and the VCR's circuitry will allow recording in the S-video mode. Conversely if the I.D. hole is not present in the cassette the same limit switch is actuated when the cassette is loaded and S-video recording is not allowed by the VCR's circuitry.
People who use these S-video VCRs often purchase standard format cassettes (VHS, 8 mm or VHS-C) and add the S-video record enable I.D. hole to these same cassettes to allow these same cassettes to be recorded in the S-video mode (SVHS, Hi8 or SVHS-C). These same people are motivated do this for reasons of convenience and economy since S-video cassettes are less commonly available and more expensive. These same people consider the resulting videotape recordings generally acceptable for their intended use.
The practice of forming the S-video record enable I.D. hole in standard videocassettes by obvious and haphazard methods is inconvenient and inaccurate at best and hazardous at worst. The same practice is hazardous because lack of control may cause damage to the cassette and more importantly because debris which is created when forming the S-video record enable I.D. hole may be forced into the videocassette and ultimately come in harms way with regard to the video tape or the videocassette and VCR mechanisms.
An object of the present invention is to facilitate forming the S-Video record enable ID hole in standard videocassettes while avoiding damaging the cassette or letting loose debris enter the cassette. The present invention in its preferred embodiment can be used to form the S-video record enable hole in any VHS, 8 mm or VHS-C cassette. The same hole is formed by either cutting, piercing or melting through the plastic cassette casting.
A further object of the present invention is to provide accurate and automatic positioning for the hole forming implement when the same hole is being formed. This is accomplished by means of positioning plates one side of which fits to the videocassettes in a specific and singular way. One of these positioning plates is formed such that it provides said positioning for both VHS and 8 mm videocassettes. These same positioning plates contain guide bushings for properly positioning the hole forming implements while the holes are being formed. Said bushings are made of materials appropriate to the hole forming method employed and have a deliberately controlled length through the bore so as to control the depth to which the hole forming implement will penetrate the videocassette.